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 * Copyright (c) 1998, 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.awt.font;

/**
 * The <code>LineMetrics</code> class allows access to the
 * metrics needed to layout characters along a line
 * and to layout of a set of lines.  A <code>LineMetrics</code>
 * object encapsulates the measurement information associated
 * with a run of text.
 * <p>
 * Fonts can have different metrics for different ranges of
 * characters.  The <code>getLineMetrics</code> methods of
 * {@link java.awt.Font Font} take some text as an argument
 * and return a <code>LineMetrics</code> object describing the
 * metrics of the initial number of characters in that text, as
 * returned by {@link #getNumChars}.
 */


public abstract class LineMetrics {


  /**
   * Returns the number of characters (<code>char</code> values) in the text whose
   * metrics are encapsulated by this <code>LineMetrics</code>
   * object.
   *
   * @return the number of characters (<code>char</code> values) in the text with which this
   * <code>LineMetrics</code> was created.
   */
  public abstract int getNumChars();

  /**
   * Returns the ascent of the text.  The ascent
   * is the distance from the baseline
   * to the ascender line.  The ascent usually represents the
   * the height of the capital letters of the text.  Some characters
   * can extend above the ascender line.
   *
   * @return the ascent of the text.
   */
  public abstract float getAscent();

  /**
   * Returns the descent of the text.  The descent
   * is the distance from the baseline
   * to the descender line.  The descent usually represents
   * the distance to the bottom of lower case letters like
   * 'p'.  Some characters can extend below the descender
   * line.
   *
   * @return the descent of the text.
   */
  public abstract float getDescent();

  /**
   * Returns the leading of the text. The
   * leading is the recommended
   * distance from the bottom of the descender line to the
   * top of the next line.
   *
   * @return the leading of the text.
   */
  public abstract float getLeading();

  /**
   * Returns the height of the text.  The
   * height is equal to the sum of the ascent, the
   * descent and the leading.
   *
   * @return the height of the text.
   */
  public abstract float getHeight();

  /**
   * Returns the baseline index of the text.
   * The index is one of
   * {@link java.awt.Font#ROMAN_BASELINE ROMAN_BASELINE},
   * {@link java.awt.Font#CENTER_BASELINE CENTER_BASELINE},
   * {@link java.awt.Font#HANGING_BASELINE HANGING_BASELINE}.
   *
   * @return the baseline of the text.
   */
  public abstract int getBaselineIndex();

  /**
   * Returns the baseline offsets of the text,
   * relative to the baseline of the text.  The
   * offsets are indexed by baseline index.  For
   * example, if the baseline index is
   * <code>CENTER_BASELINE</code> then
   * <code>offsets[HANGING_BASELINE]</code> is usually
   * negative, <code>offsets[CENTER_BASELINE]</code>
   * is zero, and <code>offsets[ROMAN_BASELINE]</code>
   * is usually positive.
   *
   * @return the baseline offsets of the text.
   */
  public abstract float[] getBaselineOffsets();

  /**
   * Returns the position of the strike-through line
   * relative to the baseline.
   *
   * @return the position of the strike-through line.
   */
  public abstract float getStrikethroughOffset();

  /**
   * Returns the thickness of the strike-through line.
   *
   * @return the thickness of the strike-through line.
   */
  public abstract float getStrikethroughThickness();

  /**
   * Returns the position of the underline relative to
   * the baseline.
   *
   * @return the position of the underline.
   */
  public abstract float getUnderlineOffset();

  /**
   * Returns the thickness of the underline.
   *
   * @return the thickness of the underline.
   */
  public abstract float getUnderlineThickness();
}
